Applicators for the manual application of a film to a substrate utilizing the principles described above are, in turn, described in the German patent document 37 36 367 and the corresponding U.S. copending application identified above.
The device described in this latter application has small dimensions and is easily handled by the user and can provide an accurate positioning, easily ascertained orientation and covering of the substrate with a film peeled from its carrier foil as that film is pressed by the foot against the substrate.
The supply spool may be provided in a rapid-replacement cassette in the latter device and the take-up spool may be driven by the rotation of the supply spool as the ribbon or strip is drawn across the substrate which is usually a paper sheet.
The film which is transferred to the substrate can be an adhesive film which can be constituted of a contact or pressure-sensitive adhesive enabling photographs or other items to be mounted on the substrate through the intermediary of the adhesive film.
The transferred film may be a cover or correction film which can be opaque to cover incorrect printing or typing, for example, and may thus have a color corresponding to the color of the substrate to which it is applied. The use of a hand-held device for applying such cover films, allows whole lines of typewriting symbols to be covered and overtyped if desired.
Conventional hand-held devices have been used primarily for application of adhesive films to the substrate. In general when a cover film is to be applied, problems are encountered which may not be present when an adhesive film is to be provided, due primarily to irregularities in the surface of the substrate.
In general, the adhesive film is somewhat flexible and tacky so that it adheres readily to the substrate even when the substrate may manifest surface irregularities in the form of rises or depressions. With a cover film, however, irregularities which may result from surface distortions, differences in yielding characteristics of the substrate when the foot is pressed thereagainst and irregular surfaces below the paper sheet serving as the substrate, or the like, may result in transfer of the cover film only from part of the carrier foil, irregular emplacement of the cover film on the substrate and less adhesion of the cover film, where transferred from the carrier foil, in some places than in others.
As a consequence, there may be strip-like or local retention of the cover film on the carrier foil or only an irregular or intermediate emplacement of the cover film on the substrate as a consequence of these irregularities.
Typical of a result which one finds in earlier systems for the application of such cover films is that depressions or recesses in the path of movement of the device may remain uncovered by the film while high points are indeed capable of stripping the cover film from the carrier foil, thereby providing an irregular pattern in the application of the cover film to the substrate.